Process of producing alkaline-earth molybdates in lumps



5...... Mal-13.19.13 2,241,742

' UNITED" STATES PATENT raocnss or raonucmo AIKALINE-EARTB MOLYBDATES m LUMPS Gustav Sehiiphaus, Hamburg-Harburg, Germany No Drawing. Application December, 15, 1938,

OFFICE Serial No. 245,983. In Germany July 14, 1938 (Ci. 75 -l33) 12 Claims.

This invention relates to av process of producing alkaline-earth molybdates in lumps.

In the production of molybdeniferous special irons and steels ferromolybdenum is increasingly replaced by combinations of molybdic acid with other metals, preferably metals of the alkalineearth group like calcium. The molybdenum content of these molybdenum compounds is ,re-

duced by the liquid iron to metallic molybdenum which is absorbed by the iron.

The use of these compounds aifords considerable advantages compared with that of ferromolybdenum, since they can be produced in a substantially purer form, particularly without carbon content, and the cost of production is much lower than that of fer'romolybdenum. The present state of the art with respect to producing compounds oi molybdic acidand alkalineearth metals is. however, open to the objection that they are obtainable only in pulverulent form and not in that of solid lumps of larger size.

.When a hot iron or steel bath is charged with this fine powder, .much dust develops and involves a considerable loss of expensive molybdenum compounds, in consequence whereof most of the economic advantages realized by the re-' placement of ferro alloys are lost again.

It has been proposed to moisten a'mixture of molybdic acid and calcium carbonate, to press the paste, to dry the pieces thus obtained and to feed them to the iron or steel bath. Subjected to the heat of the furnace, this mixture will form calcium molybdate. However, as molybdic acid becomes volatile if exposed to heat, a portion thereof will be lost. Furthermore, since the firm structure of the pieces or lumps is eliminated due to the escape of the carbonic acid, they will crumble, so that the result is substantially the of the molybdic acid compounds as well as their addition to an iron or steel bath are effected without any loss of valuable metal.

From the raw material containing molybdenum, molybdic acid is obtained in known manner whose content of constituents detrimental to iron or steel is within permissible limits. The molybdic acid is thoroughly mixed with the hydroxide of an alkaline-earth metal, as calcium hydroxide, in the stoichiometric ratio corresponding to the normal or an acid molybdate (polymolybdate), with a slight addition of water if necessary, and pressed in suitable molds by the application of great pressure. The pressed pieces thus obtained are hardened by drying,

and there occurs an extensive combination of molvbdic acid and alkaline-earth hydroxide while neutral or acid molybdate (polymolybdate) is formed.

To provide for the complete chemical conversion of the molybdic acid and alkaline-earth hydroxide and to insure greater hardness and strength of the pressed pieces it is advisable to soak the latter with water. This can be done by placing them for some time in a vessel filled with water and thereupon drying them in a suitable apparatus while subjecting them to heat so as to cause evaporation of the water, or by treating them in a hardening boiler with steam under pressure, or by exposing them in a suitable vessel to the action of a current of superheated steam.

From the mechanical mixture of the two substances a chemical compound is thus produced which retains the original outer shapeof the pressed piece and possesses, extraordinary mechanical strength. The hardened pressed piece does not crumble even when exposed to the high temperatures of an iron or steel bath, so

that loss due to dusting is excluded.

The peculiar advantage afforded by the process according to the invention is that the lumpy shape is not brought about by means of an additional binding agent but by converting the mechanical mixture of 'two substances into a chemical compound.

In the same way neutral and acid molybdates (polymolybdates) such as may be obtained, depending on the mixing proportion of molybdic acid and calcium hydroxide or of the hydroxide of another alkaline-earth metal, for instance of barium or strontium.

The pressed pieces are preferably produced so as to have equal molybdenum contents to facili-- tate their subsequent use.

containing 64.4%

These pressed pieces consisting of neutral or acid molybdates (polymolybdates) of alkalineearth metals may be produced also in the same manner but with an addition of silicic acid, as

quartz sand, by uniformly distributing the sand in the mixture formed-of molybdic acid and alkaline-earth hydroxide prior to molding and pressing. Owing to the presence ofsilicic acid in the pressed piece consisting for instance of calcium molybdate the formation of calcium silicate becomes possible after the melting and reduction of the molybdic acid, which with respect to its lime and silica content corresponds to steel furnace .slag.

The following examples show' the performance of the invention: I

Example 1 For the production of normal calcium molybdate CaO.Moa, 90 g. of commercial molybdic acid containing 64.4%=57.96 g. Mo are mixed with 456g. of commercial 98 per cent. calcium hydroxide=44.69 g. Ca(OH)z and moistened with mm. water. after the mixture has been subjected to considerable pressure and the pressed piece hardened for about two hoursbyflowing steam superheated to approximately 170 C., the resulting piece has a weight-of 124.73-

g. and contains 46.46% M0=5'7.95 g. Mo.

Example 2 Example 3 A pressed piece composed of acid calcium molybdate and silicic acid is obtained by mixing 90 g. molybdic acid containing 64.4% Mo=57.96 g. Mo, 15.2 g. commercial 98 per cent. calcium hydroxide=14.9 g. Ca(OH)z and 22.6 g.

quartz sand and making a mixture therebfwhile adding 5 ccm. water. The moist mixture is pressed in molds by applying considerable pressure. The pressed piece is then hardened by subjecting it for instance for two hours to the action of superheated flowing steam. in this way a pressed piece weighing 124.3 g. and containing 46.63% Mo=57.96 g. M0 is obtained.

The expression an alkaline-earth molybdate, occurring in the appended'claims, is intended to finclude normal or neutral molybdates as well as acid molybdates or polymolybdates.

The expression molybdic acid" occurring in v the appended claims is intended to include molybdic acid itself as well' as molybdenum trioxide, M003, the anhydride of molybdic acid.

I claim: v

1. Process for producing a hard mass containing an alkaline-earth molybdate which comprises subjecting a slightly moist mixture com-v prising molybdic acid and an alkaline-earth hydroxide to high pressure to form a compacted mass from said mixture and thereafter subjecting .the compacted mass to treatment which causes interaction between molybdic acid and alkaline-earth hydroxide with the formation of an alkaline-earth molybdatqwhich interaction is accompanied by hardening of the compacted mass. 1

2. Process for producing a hard mass containing an alkaline-earth molybdate which comprises subjecting a slightly moist mixture comprising molybdic acid and' an alkaline-earth hydroxide to high pressure to form a compacted mass from said mixture and thereafter contacting said c'ompacted mass with steamto harden it.

3. Process for producing a hard mass containing an alkaline-earth molybdate which comprises subjecting a slightly moist mixture comprising molybdic acid and an alkaline-earth hydroxide to high pressure to form a compacted mass from-said mixture and thereafter contacting said compacted 'mass with steam at a temperature above C.

4. Process for producing a hard mass containing an alkaline-earth molybdate which comprises subjecting a slightly moist mixture comprising molybdic acid and an alkaline-earth hydroxide to high pressure to forma compacted mass from said mixture, wetting said compacted mass with water and thereafter drying the wetted compacted mass.

5. Process for producing a hard mas s containing an alkaline-earth molybdate which comprises subjecting a slightly moist mixture comprising molybdic acid and'an alkaline-earth hydroxide to high pressure to form a compacted mass from said mixture, soaking said compacted mass with 1 water and thereafter drying the mass.

6. Process for producing a-hard massicontaining an alkaline-earth molybdate which comprises subjecting a slightly moist mixture comprising molybdic acid, an alkaline-earth hydroxide and silicon dioxide to high pressure to form a compacted mass from said mixture and thereafter subjecting the compacted mass to treatment which causes interaction between molybdic acid and alkaline-earth hydroxide with the forma-.

tion of an alkaline-earth molybdate, which-interaction is accompanied by hardening of the compacted mass, the alkaline-earth oxide and silicon dioxide ratio of said mixture corresponding to such ratio of steel furnace slag.

7. Product produced according to claim 1. 8. Product produced vaccording to claim 6. 9. Process for producing a hard mass containing an alkaline-earth molybdate which comprises subjecting a slightly moist mixture comprising molybdic acid .and an alkaline-earth hydroxide to high pressure to form a compacted mass from said mixture and thereafter subjecting the comlumps containing alkaline-earth molybdate, the

step which comprises subjecting a slightly moist mixture comprising molybdic acid and an alkaline-earth hydroxide to great pressure to form a compacted mass from said 'mixture.

GUSTAV s'cHiJPHAUs. 

